Force 120 rebuild trying to jump start

[Craighimself]

Took my 97 sport jet powerhead apart, replaced block and exhaust manifold, I have everything back together and Im trying to test start on bench before I put back in the boat.

I'm putting power to black and yellow assuming this is the run circuit then tapping yellow/red to kick the starter over.. No spark.

Cranking slowly from new rings and tight compression. but still 150 rpm.

What needs power for this thing to run???

I bought this boat in a heap so no keyswitch or harness or anything

 

[Frank Acampora]

Re: Force 120 rebuild trying to jump start

mercury ignition is very much like a magneto. At 150 RPM, the flywheel is just not turning fast enough to charge the CD box. You need to get it to crank up around 300-350 to generate a spark.

The ignition is self energising so if the kill circuit is not connected the engine will start and run.

 

[pnwboat]

Re: Force 120 rebuild trying to jump start

Even with new rings it should spin like any seasoned engine. Either bad battery connection, bad starter solenoid, bad starter, or something binding up in the motor. What size rings were installed?

 

[Craighimself]

Re: Force 120 rebuild trying to jump start

Quicksilver rings on stock bore, its a compression bind so its a good thing. I can take the plugs out and it spins fast as hell The problem is I don't know if the no spark is coming from bad connections or if something on the plug needs to be powered up besides the yellow/red wire.

at the plug I have:


black/yellow that should be the kill circuit
purple from the trigger that splits goes to coil 1 and switchbox
tan/blue goes to temp sensor on head
black goes to ground
grey goes to switchbox
yellow/black goes to auto enricher
red/purple center pin has 12v

what needs voltage for this thing to start? I have tried a few different combos but i don't want to move backwards by shorting things out.

Anyone know what needs battery voltage to run the engine, it can't be just power to starter and the thing runs can it?

 

[Frank Acampora]

Re: Force 120 rebuild trying to jump start

As I said above: It is like a magneto ignition. It is self energising and does not need any source of outside voltage. At about 300 RPM the flywheel magnets are spinning fast enough to generate enough voltage in the stator to charge the CD box(es) capacitors. If the kill circuit is not connected, the engine will start and run.

The kill circuit shorts the capacitors in the CD box (CDI: Capacitor Discharge Ignition) to ground instead of letting them discharge into the coil, and no spark is generated.

Battery voltage is used on the starter, overheat indicator, and gauges.

 

[pnwboat]

Re: Force 120 rebuild trying to jump start

Did you say you were putting 12 volts to the Black/Yellow Kill circuit wire? There should be no voltage on that wire. All that wire is for, is to ground out the CDM modules to kill the spark when you turn the ignition key off, or pull the kill switch lanyard off.

 

[Craighimself]

Re: Force 120 rebuild trying to jump start

Yes I put voltage to black and yellow. I cant get this to spark with black and yellow open and just powering the yellow/red wire.

Has anyone gone through the wiring on this thing. Im getting 6v from green/white and 6v from white/green when its spinning. black/yellow circuit has 2v on it maybe.

how can i test my stator and trigger to make sure were making the wright volts

 

[jerryjerry05]

Re: Force 120 rebuild trying to jump start

Turning over great with no plugs??
You need to make sure the connections are good.
Then do a compression test.
Outboardignition.com or cdielectronics.com to test the stator/trigger.
Did the parts box have the key switch or cable?

 

[pnwboat]

Re: Force 120 rebuild trying to jump start

To test the stator, you can measure the resistance. If you have a red stator, check between the White/Green and Green/White wires. Should read 500-700 Ohms. Since this came out of a Sportjet, do you know if it happens to have a Rev. limiter on it?

 

[Craighimself]

Re: Force 120 rebuild trying to jump start

I checked resistance to the stator it was 670 within range,

To each of my coils I measure 9v ac across the hot and ground

Stator seems to make 40v ac while spinning.

Both rev limiter and kill switch eliminated the black and yellow wire is unplugged

No signs of wire damage.

Is this enough voltage to the coils? I don't have a DVA so i cant measure the peak but power going there seems like it should show some sign of life.

I guess it would be reasonable to assume that all 4 coils are bad?

 

[pnwboat]

Re: Force 120 rebuild trying to jump start

I don't think I would assume that at all. There are some resistance test you can do on the CDM's themselves. If you look at the 4 pin modular connector on each of the CDM units, you'll see the letters A,B,C,D on the modular plug that is removable. Each letter corresponds to a wire/pin on the CDM.
Position "A" is the black wire or GROUND.
Position "B" is the Black/Yellow or engine Kill Circuit.
Position "C" is the trigger signal. Purple Cyl#1, White Cyl #2, Brown Cyl#3, Blue Cyl#4.
Position "D" is stator voltage. Either Green/White or White/Green depending on which cylinder.

Remove the 4 pin modular connector. Look into the socket in the CDM and you will see 4 male pins. With you meter, measure between the following pins:

1. Primary coil winding resistance between "A" and "C". Should be around 1240 Ohms.
2. Secondary coil winding resistance. Remove the coil wire from the CDM by unscrewing it. Yes it just twists off exposing a threaded post. Measure between the post and "A". Should be around 980 Ohms.

You need a "DIODE" setting on your meter to read the following. If not you will get some strange readings. With the meter leads in one direction, you see high resistance, reverse the leads and you'll see not as high resistance, but it will slowly increase as you hold the leads in place.

3. "D" to "A" Should read like a diode on the diode setting. Open one direction, reverse the leads it should read about 600 Ohms.
4. "D" to "B" Should also read like a diode on the diode setting. Open one direction, reverse the leads it should read about 600 Ohms.

Hope this helps.

 

[Craighimself]

Re: Force 120 rebuild trying to jump start

Thanks a bunch for the tests..

CYL1 A-C =1084 A-wire screw = 1041 D-B=620 D-A= 638
CYL2 A-C = 1084 A-wire screw = 1038 D-B=583 D-A=600
CYL3 A-C=1086 A-Wire Screw= 1040 D-B=550 D-A= No reading
CYL4 A-C 1078 A- Wire Screw= 1040 D-B=585 D-A= 615

I was testing last night and I couldn't get any reasonable reading of AC power from the stator testing the green and white to each other and then to ground. I swear I read 4-8 volts AC or it, but I am not sure what type of current I should see here. I pulled the flywheel and stator off to inspect. It looks good to me, but then again Ive never had the opportunity to see a bad one.

I cleaned the magnets on the flywheel there are still vertical lines burnt in pretty small.

The trigger has small cracks around the perimeter

 

[pnwboat]

Re: Force 120 rebuild trying to jump start

Looks like you may have a problem with the #3 CDM. You can address that later. Measure between the Green and White stator wires. Should be between 500 - 700 Ohms.

When you go to start it, the only connections you need are ground cable from battery to block. Positive cable from battery to the large post on the starter solenoid. That is the large post across from the one that goes to the starter. To start the motor, or check for spark, momentarily short the small terminal with the yellow wire (I think it's yellow) to the big terminal on the solenoid that goes directly to the battery. The ignition system is self energizing. Once the flywheel starts to spin, the stator will generate voltage to the CDMs which will generate spark to the plugs. I think I would also try leaving the modular plug on #3 CDM disconnected to see if that has any affect on the spark on the other plugs.

To stop the motor if it starts, just take your hands and cover the carburetor openings to "choke" the motor. Or you can take a small jumper wire and connect all of the Black/Yellow wires from the CDMs to one end of the wire. To stop the motor, take the other end of the wire and touch it to the block. This will ground out the ignition signal to the CDMs.

 

[Craighimself]

Re: Force 120 rebuild trying to jump start

660 between green and white on the stator, Im going to bolt it back together and test again.

 

[Craighimself]

Re: Force 120 rebuild trying to jump start

So cleaned up flywheel, stator and trigger re-installed, checked resistance on green to white 660, then checked again after it was plugged in and it went down to 550. started unplugging cdi harnesses until on #3 and there it goes back to 660.

And as in the diode test thanks to pnwboat I was sure coil 3 had a problem

kept #3 un-plugged cranked it and saw what I had been dreaming about for so long, SPARK!!! Cyl1 was SPARKING!! I was so excited i naturally bumped the metal table and shocked myself, but it actually felt good.

Plugged yellows into the switchbox still sparked
plugged black/yellow into rev-limiter no spark
Unplugged rev limiter, installed plugs, strapped engine down to table opened carbs, cranked it and FIRE!!!!

my neighbors came over to see what the ruckus was, I said "that my friends is the sound of sucess!!!"

now Im hoisting the engine into the boat, got a coil on order, ill be in business in no time.

pnwboat= thanks a bunch I would have bought a whole new ignition system without your help.

 

[pnwboat]

Re: Force 120 rebuild trying to jump start

Ahh yes, the sweet sound of success!